1. Field of the Invention
The present invention relates to the field of submersible pumping systems for producing fluids, such as petroleum and gas, from wells. More particularly, the invention relates to a technique for producing fluids from wells by means of a submersible pumping system coupled to a packer through which a plurality of fluid passages are formed. The passages permit oil and gas to be produced through the separate passages of the packer, and through fluid conduits and annular portions of the well above the packer. The invention also provides a technique for sensing parameters in the vicinity of a submersible pumping system by means of the packer, as well as for injection of chemicals and other substances through at least one of the passages formed in the packer.
2. Description of the Related Art
A variety of pumping systems have been devised and are currently in use for raising fluids from wells, such as petroleum production wells. In general, where a subterranean formation provides sufficient pressure to raise wellbore fluids to the earth's surface, the well may be exploited directly, by properly channeling the fluids through conduits and above-ground valving. However, where the subterranean formations do not provide sufficient pressure, submersible pumping systems are commonly employed for forcing wellbore fluids to the earth's surface for subsequent collection and processing.
In general, one class of submersible pumping systems includes a prime mover, typically an electric motor, coupled to a pump. The electric motor and pump are positioned within wellbore fluids and the pump is driven by the electric motor to draw the fluids into the pump and to force them, under pressure, to the earth's surface. The fluids produced by the pump may be forced upwardly through various types of conduit, such as the well casing, or production tubing, to a collection point at the earth's surface. The pumping systems may also include ancillary components, depending upon the configurations of the subterranean formations. Such components often include motor protectors for preventing wellbore fluids from mixing with fluids contained in submersible electric motors, separators for removing oil from water or gas, and injection pumps or compressors for reinjecting water or other non-production fluids into designated subterranean formations above or below the producing horizons.
In conjunction with well completion equipment, such submersible pumping systems often provide reliable means for raising production fluids, and for processing the fluids in situ. However, they are not without drawbacks. For example, submersible pumping systems configured to separate production fluids from gas are typically designed to convey oil through a central production conduit or tubing, and gas through an annular area surrounding the tubing. However, flow rates available from the pumping system may be severely limited by head losses through the tubing. In general, such head losses are a function of the length of the tubing, the tubing diameter, the fluid flow rate, and physical characteristics of the tubing surfaces. To supply adequate fluid displacement through stands of production tubing, the pumping systems may be adapted to provide enhanced pressure head, such as by increasing the number of stages in the pump. However, providing additional stages and output head from the pump generally also requires an increase in the size or rating of the electric motor used to drive the pump, along with an increase in the size or rating of power cable supplying electrical energy to the motor, ultimately resulting in increased cost and power consumption.
Other drawbacks of existing submersible pumping systems stem from their limited ability to accommodate intermittent data acquisition, chemical injection and other processes, useful from time to time in exploiting the subterranean formations. In particular, while certain instrumentation is commonly provided as a permanent part of the pumping system itself, it may be desirable in certain applications to sense wellbore or pumping system parameters only on an "as needed" bases, such as by lowering retrievable instrumentation into the well for data collection. However, this is often difficult or impossible in conventional pumping system applications, particularly where packers are used in conjunction with the pumping system or fluid conduits to isolate regions of the wellbore from one another. Such packers are typically set prior to actuation of the pumping systems, and cannot be easily traversed once the pumping system is in operation.
Similarly, it is sometimes desirable to inject chemicals or fluids in the vicinity of a subterranean formation, upstream or downstream of a submersible pump during operation. Such fluids may include anticorrosive agents, viscosity reducing agents, scale inhibitors, and so forth. However, unless dedicated chemical injection lines are provided in the pumping system during its deployment, such injection is often difficult or impossible to accommodate without removal of the pumping system from the well.
There is a need, therefore, for an improved technique for completing a fluid producing well which avoids or attenuates these drawbacks of existing systems. In particular, there is a need for a submersible pumping system capable of producing wellbore fluids more efficiently than through the production tubing techniques employed in conventional systems. There is also a need for a pumping system which can flexibly accommodate oil and gas production at efficient power levels while permitting special instrumentation, chemical injection, and other processes to be carried out on an intermittent basis without disrupting operation of the pumping system.